Hi,
Vsevolod Stakhov via mailop wrote on 21.10.24 at 21:56:
In fact, Rspamd itself could do that downgrade, meaning setting CTE to
7bit and recoding all relevant parts to qp/base64 (depending on their
content) before DKIM signing. It is all perfectly doable with the
existing Rspamd Lua API I suppose. Of course, Milter connector also
allows full body rewrite as well as specific headers rewrite. It just
requires some manual coding.
Some clients can also be 'fixed' to use 7bit only: https://
support.mozilla.org/en-US/questions/1272196
In general, it is the never ending issue of the middleboxes in the
Internet. You can't simply assume that all peers on your way support
even 30+ years old standards. Introducing something that breaks E2E
compatibility (a good example of such a thing is clearly SMTPUTF8) has
always been risky in terms of deliverability.
The least common denominator is just to use 7 bit and refrain from using
any sort of IDN names.
right now, I ponder to have a dedicated Postfix instance for delivering
to Mimecast, either with the force_mime_input_conversion option enabled,
or 8BITMIME disabled. I understand that downgrading/converting all mails
to 7bit also can have disadvantages.
I learned something new with all this... :)
Florian
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